fix(cargo-bazel): ignore example crates when checking if proc-macro (bazelbuild#2596)

# WHAT

* ignore example crate types when checking if it is a proc-macro

# WHY

When building the list of `deps` and `proc_macro_deps` for a given
crate,
dependency crates which contain examples in their Cargo.yaml of of type
`proc-macro` cause the dependency to be added to the `proc_macro_deps`.
The
example crate types should be ignored.

Fixes bazelbuild#2577

Co-authored-by: UebelAndre <[email protected]>

Author: qtica

crate_universe/src/metadata/dependency.rs

@@ -197,10 +197,10 @@ fn is_lib_package(package: &Package) -> bool {
 }
 
 fn is_proc_macro_package(package: &Package) -> bool {
-    package
-        .targets
-        .iter()
-        .any(|target| target.crate_types.iter().any(|t| t == "proc-macro"))
+    package.targets.iter().any(|target| {
+        target.crate_types.iter().any(|t| t == "proc-macro")
+            && !target.kind.iter().any(|t| t == "example")
+    })
 }
 
 fn is_dev_dependency(node_dep: &NodeDep) -> bool {
@@ -425,6 +425,30 @@ mod test {
             .unwrap()
     }
 
+    #[test]
+    fn example_proc_macro_dep() {
+        let metadata = metadata::example_proc_macro_dep();
+
+        let node = find_metadata_node("example-proc-macro-dep", &metadata);
+        let dependencies = DependencySet::new_for_node(node, &metadata);
+
+        let normal_deps: Vec<_> = dependencies
+            .normal_deps
+            .items()
+            .into_iter()
+            .map(|(_, dep)| dep.target_name)
+            .collect();
+        assert_eq!(normal_deps, vec!["proc-macro-rules"]);
+
+        let proc_macro_deps: Vec<_> = dependencies
+            .proc_macro_deps
+            .items()
+            .into_iter()
+            .map(|(_, dep)| dep.target_name)
+            .collect();
+        assert_eq!(proc_macro_deps, Vec::<&str>::new());
+    }
+
     #[test]
     fn sys_dependencies() {
         let metadata = metadata::build_scripts();

crate_universe/src/test.rs

@@ -139,6 +139,14 @@ pub(crate) mod metadata {
         .unwrap()
     }
 
+    pub(crate) fn example_proc_macro_dep() -> cargo_metadata::Metadata {
+        serde_json::from_str(include_str!(concat!(
+            env!("CARGO_MANIFEST_DIR"),
+            "/test_data/metadata/example_proc_macro_dep/metadata.json"
+        )))
+        .unwrap()
+    }
+
     pub(crate) fn git_repos() -> cargo_metadata::Metadata {
         serde_json::from_str(include_str!(concat!(
             env!("CARGO_MANIFEST_DIR"),

crate_universe/test_data/metadata/example_proc_macro_dep/Cargo.lock

@@ -0,0 +1,14 @@
+[package]
+name = "example-proc-macro-dep"
+version = "0.1.0"
+edition = "2018"
+
+# Required to satisfy cargo but no `lib.rs` is expected to
+# exist within test data.
+[lib]
+path = "lib.rs"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+proc-macro-rules = "=0.4.0"